A bit of what you should know about event power and electrical safety

Ted Pallas contacted us and wanted to create a short primer on power, in response to the terrible fire at Ghost Ship in Oakland, CA. Any fire anywhere is a reminder that knowledge of electricity, how it works and how it impacts safety, is essential to any of us organizing or playing electronic music live. This won’t provide everything you need to know, by a longshot, but it’s a good step toward knowing a bit more, and I hope we continue taking those steps together in future.

The rub of electronic music and visual media is that both performance and practice require electricity. Electricity can come from a number of places – it can come from the wall, or a generator, or a battery or a laptop. Electricity can also come in a variety of flavors – high voltage, low voltage, 120, 208, 277 and 480, single phase and multi phase…there’s a lot to know and a lot to keep straight.

Before we get into all the stuff there is to know we’d like to make it clear that ignoring power requirements jeopardizes budgets, guest safety and artist safety. The best case for a power disaster is “everyone thinks the promoter is a joke.” The worst case is “everyone is dead.” There’s no mincing words – as a producer you have an obligation to your audiences, your artists and your vendors that includes not only being safe but also not jeopardizing the health of the scene.

Planning gear and power consumption

When configuring/pre-producing an event there are two ways to approach power – what do I want to bring vs what power is available on-site. I typically like to start with the former – I tend not to repeat venues so much, so rather than re-do step 1 every time I party I can just start with some gear that I know. From a power consideration you want to look at how many amps a given piece of gear draws.

Let’s do an exercise together – we are going to total up power consumption for a small sound package and some lights. Here’s the spec sheets we will be referencing:

When we think about powering coming out of a wall we are going to be thinking in Amps – we are getting such-and-such many amps off of a given circuit. The JBL spec sheets are easy – they give us draw in Amps. You’ll note there’s a (120v) call-out – this is because Amperage is a function of voltage and wattage. If yr wall power is not 120v – if you are not in the United States – you will get a different Amp draw. Let’s say our rig has two subs, two tops for mains and an added top for DJ monitoring. At 1/3rd power we’d be drawing 2.03amps, so I’m going to round us up to 3A in case we really need to push volume that night. All these boxes share the same amp circuit, so the math is easy – we need a total of 15A coming out of a wall circuit to power our soundsystem, as we need 13.5A without the padding.

Now let’s do lights. Our not-Sharpy’s (the Spot 2’s) are going to draw 108W. To turn that into Amps we divide the Known Wattage by the (Known Voltage times the Power Factor). The power factor is essentially the oomph required by a circuit to get moving/stay moving – your phone has a low power factor, a motor has a high power factor. If you don’t know power factor a good rule of thumb is “0.8”.

So now the math:

Amps = 108W / (120v*0.8) = 1.125 Amps

On a 15 amp service/circuit we can comfortably fit 12 lights.

Multimeters and testing

Now we need to get to the venue and see what we’ve got to work with, and to do this we will need a Multimeter.

Ed.: The following advice may not be for everyone. There are three ways to go about this. On a basic level, many venues and certainly permanent venues will have accurate information on-hand about power availability. That means you may not have to test anything. If that isn’t available, you can do a simple test. John McIntyre, an electrician writing in CDM comments, suggests the following:

IMHO, skip the multimeter and buy a 10 dollar outlet tester, the kind that plugs into a wall outlet with 2 yellow lamps and one red lamp in the handle. You can find them at any decent hardware store in the electrical tools section. This will help you make sure your outlets are wired with the correct polarity and that your ground connection is intact back to the electrical panel.

The most advanced option, if you need to know exactly what’s there and don’t have information, is to use a multimeter. But this isn’t like the multimeter you might use in electronics projects – because you’re plugging into a wall, not low voltage. That creates additional safety concerns, so read carefully. A RadioShack multimeter used for your Arduino projects is likely to fail catastrophically, and commenters are right that we should be clear that this isn’t what we’re suggesting.

If you produce events and you don’t have a multimeter – get a multimeter, and make sure it can measure enough amperage to meet your needs. Don’t skimp here – a $45 multimeter will not serve you. Ask the people at the store to help you choose one that meets your local power needs.

There’s a couple options present for measuring an outlet – you can measure voltage, or you can measure amps. Measuring voltage will ensure that the outlet you’re testing is properly connected back to the main breakers. Measuring amps is a bit more tricky, and not necessary if you don’t intend to use the majority of the power available on a given circuit. This is why it’s important to measure the amp requirements of your gear using the available specification sheets.

If you need to measure amps you need to have specialized equipment, and you need to follow a special process. If you’re uncomfortable being around large amounts of power consider calling an electrician. You’re going to be looking for a big beefy multimeter with a clamp on top. This clamp goes on the wire on the back of the outlet OR the wires coming out of the breaker box. You have a friend plug in a fan or something similar (another cheap motor) on the plug-in end of the outlet, and then you’ll see your amperage. You’ll want to measure amperage if you’ve got reason for concern – typically this will be a bar fridge or an HVAC system who’s power source isn’t known by the venue. You don’t want your soundsystem sharing a circuit with other big/beefy power draws. If the venue knows what circuits everything is on you’re more than likely in the clear on needing to measure amperage.

Read the instructions that come with your multimeter. Before you use it in a venue experiment with the multimeter at home, on a circuit with nothing of value plugged in. Multimeter use is a skill like any other – you can do it right, or you can do it wrong. In this case “doing it wrong” will lead to tripped breakers or nasty zaps. If you’re uncomfortable learning this skill it’s best to call an electrician and have hem meet you at the venue.

Measure the outlets in the space, and if you have breaker access/it’s acceptable to the venue start confirming that outlets are on a given circuit by throwing breakers. Follow this up with a visual inspection of ALL wiring. If you see any bare metal this is an unsafe venue. If you see outlets with multiple power strips you want to be wary, and you should investigate to see if it’s possible to unwire the multiple strips and more evenly distribute needs. If you see hot cable (carrying a current) on the ground see if the cable can go in the air. (In general – “no cable on the ground ever under any circumstances” is my rule of thumb. There are times when this rule needs to be broken, in these instances use either a cable ramp or a ton of gaffers tape to secure the cable. If you can avoid crossing a walkway with power by adding more cable and running longer this is something worth considering.) If you see cable running alongside/on/underneath home-built wooden infrastructure consider booking an alternative venue.

While inspecting outlets you’ll want to look for obvious damage – wiggling sockets, a ton of scratches and scorch marks are all good reasons to skip a given outlet.

When actually loading-in make sure you have enough extension cable to get power from the wall to where it’s needed. Don’t swag cables, or let them pull tight. Don’t pull tight against connectors. Tape down everything that needs to be taped down, and tape it down well with gaffer’s tape. Tie up everything in the air, especially crossing a door or other walkway path. Do not tie anything to a water pipe or a sprinkler pipe – these pipes can spring leaks, and you don’t want a leak running along your power lines.

Wires and electrical safety

Some good points too from John McIntyre in comments:

Don’t go cutting the ground on your extension cables in order to plug something in. Grounds are a critical component of electrical safety. For similar reasons you should avoid putting a ground lift in line with gear – if you really need to lift the ground on your soundsystem do it at the XLR connector, with an in-line XLR ground lift.

When choosing extension cables don’t go cheap – go for thick, wide-gauge cable (if you see two cables running next to each other in two separate channels put the cable back on the shelf.) You also don’t want to use more cable than you need – I always bring a selection of 25 foot, 50 foot and 100 foot Edison cables with me. This is an example of an acceptable cable for bringing power to equipment that needs a large power supply.

Signage

The last thing I’d like to leave you with is the simplest – provide lighted exit signs when your venue lacks such signs. Here’s a $16 Exit Sign. If you can’t budget this you have no business planning an event. You’ll need to modify the sign to use a plug – federal regulations require these to be wired permanently to the system. If you can swing it the best option is a self-luminescent sign – these can’t be tripped over from a dangling power cable, or unplugged by a guest with ill intentions.

Generators

Special note on generators – sometimes you need to bring your power supply with you, typically for an outdoor event. The big thing to keep in mind is that consumer generators get hot (sometimes very hot) and they are never waterproof. You’ll want to keep your generator well out of the way of your guests – they look like a good bench, but they are not a good bench. If there’s a danger of rain you’ll want to put the generator in a portable shed, or even better from a safety perspective just turn the generator off and send folks home. If you’re doing a big event – running a soundsystem, a monitor rig, a large lighting package and a front of house – you’re going to want to rent an entertainment generator. I recommend contacting Cat Power Entertainment Services directly to start your process on meeting this need. Don’t forget that generators require fuel, and you’ll need to keep an eye on consumption across your event.

A Special Note To Our European Techno Family: power voltage in your neck of the woods is generally 230V. Your Amps equation for the lights would look like Amps = 108W/(230*0.8). This solves out to 0.6A. This does not mean you can squeeze in twice as many lights! You still need to confirm that you have the amperage available coming out of the wall. Additionally you’re going to want to make sure you leave enough overhead – where I left enough for an extra fixture, in a 230V system I might leave enough for several extra fixtures.

Ted Pallas is a live event producer, media server programmer and DJ based out of Chicago, IL.

We’d like to update this guide over time. Please let us know your advice / corrections / additions in comments, and we’ll continue to update it, through the magic of the Internet.

This is terrible advice. You can’t measure the current capacity (“amperage”) out of the socket using a multimeter. You’ll either blow up the meter or the fuse, and maybe trip the circuit breaker. Even the video that’s linked only shows how to measure voltage, not current. If you know what country you’re in, you probably know voltage you’ve got. Don’t go around sticking probes into sockets.

Michael M

YES. Peter, I appreciate what you’re thinking of by running this article but it contains DANGEROUSLY BAD ADVICE. You can only measure amperage “in use”, there’s not really a way to measure the potential amperage at an outlet with a meter. You’re better off asking the venue and looking at the breaker box.

I think maybe terrible advice without further qualification / clarification. Ted went ahead and clarified why he was recommending a multimeter and which multimeters will work for this purpose.

That video was misleading, so we removed it.

Does this maybe clear things up?

JT

Peter, thanks for clarifying and editing the article. Now I understand what the intent was. I probably balked more than the typical reader because as an EE, when I saw “amperage” I interpreted that as a spec whereas “current” is a measurable quantity. Voltage is measured in volts so that ambiguity didn’t raise any alarms. Thus, to me it seemed that the article was saying you could somehow measure the current capacity out of the socket, which is impossible without tripping the breaker.

IMHO, this sentence is still misleading:
“There’s a couple options present for measuring an outlet – you can measure voltage, or you can measure amps.”
This suggests that we can measure both intrinsic properties of the outlet. Would be better to say “load current” instead of “amps” here. It’s uncommon to say you want to measure an SI unit as opposed to the quantity (e.g. do you “measure Hz” or “measure frequency”?).

John McIntyre

There are some really important things missing from this article. I’m an electrician, so naturally, a couple things came to mind while reading (tailored to USA readers):

1. Proper grounding is vital for safety. Most of your equipment will have 3 blades on the end of the cord. Never, ever, EVER snap the ground prong off to make it fit an ungrounded outlet or extension cord, and don’t use any sort of adapter to turn a 2-blade outlet into a 3 blade outlet. People die from that kind of foolishness all the time.

To add an extra level of safety, plug your equipment into a portable GFCI. They’re not very expensive, and when used properly (RTFM!), eliminate the risk of electrocution or shock.

2. IMHO, skip the multimeter and buy a 10 dollar outlet tester, the kind that plugs into a wall outlet with 2 yellow lamps and one red lamp in the handle. You can find them at any decent hardware store in the electrical tools section. This will help you make sure your outlets are wired with the correct polarity and that your ground connection is intact back to the electrical panel.

Ensuring continuity of your ground and neutral conductors will also help you prevent expensive equipment damage.

3. When selecting extension cords, go for cables with larger guages, in shortest lengths that will safely reach. The American Wire Gage (AWG) standard might be confusing because smaller numbers mean bigger wires. A 14-AWG wire is bigger than a 16-AWG wire, and that means it can safely carry more current.

In other words, if your gear is 30 feet from the outlet, a 50′-long 14 AWG cord set is way better than a 100′-long 16-AWG cord set with a big coil at one end. Smaller wire and longer runs of cable get hotter faster, especially under continuous load. In general, 14-AWG is the smallest wire you should use.

By following basic electrical safety rules, you can effectively eliminate the risk to yourself and your audience.

I think the statement about providing exit signs is on point, but be aware that the exit sign the author linked to is meant to be permanently installed on a 120VAC supply. It could probably be modified to run on a 9v battery, but I’d have to have more info on it to be able to give detailed instructions.

Codes vary by state, municipality, occupancy type, etc., but typically a venue should have at least 2 ready means of egress (escape) no matter where you are. These should be conspicuously marked, kept clear of obstacles, and properly lit. If the need for egress lighting is not met by the venue (or, if YOU are the venue) you may want to consider providing temporary lighting of these means of egress, especially on staircases and fire escapes.

Yes, part of why I wanted to get out and publish this was to solicit some additional advice. Ted has incorporated this into the article.

John McIntyre

That’s awesome! Glad to be able to help.

kevin

Thanks for sharing this advice, but please consider that “DO NOT DO X” is much harder to internalize (despite the caps-lock) than “do not do X because Y can happen”. It would be beneficial to add reasons why “hot cables” should be in the air rather than in the ground, why nothing should be tied to water or sprinkler pipes, etc.

It may be obvious to many, or perhaps SHOULD be obvious, but it doesn’t hurt to lay it out in simple terms for the rest of us (myself included).

Teetons Friar

C’mon fellas, gotta use the multimeters the good lord gave ya. Me ive got two whole ones – i call em nips.